1. Field of the Invention
The present invention relates to a functional coated product having photocatalytic activity and a process for producing the same and the use thereof.
2. Description of the Prior Art
When a photocatalyst is added to a coating material, the resulting coating is irradiated by ultraviolet light to exhibits a decomposing effect of organic substances, deodorizing effect, antifungal effect, etc.
As a coating material having such photocatalytic function, for example, a photocatalytic organic paint in which photocatalytic particles are dispersed in organic resin is known. However, the photocatalytic organicpaint has a drawback that the coating is deteriorated due to ultraviolet rays and photocatalytic function.
An inorganic paint, in which photocatalytic particles are dispersed in an inorganic composition such as a silicate, a phosphate or a zirconate, is known as a coating material having photocatalytic function. These inorganic paints have much better durability than that of photocatalytic organic paints, however, it is necessary to conduct baking at a high temperature of 200° C. or more. Therefore, the range of usage is limited, and it was not suitable for applying them directly to a construction material or plastic which has inferior heat resistance. Further, the silicate inorganic paint has also a drawback that an alkali was eluted to cause a whitening phenomenon easily.
In Japanese Patent Publication Laid-Open No. 57470/1987, an inorganic paint in which a metal alkoxide is contained is disclosed. This inorganic paint is cured at a temperature of not more than 200° C., however, the coating does not have flexibility and there was a problem that crack easily occurred.
Recently, with a necessity to apply a paint to various materials, a low-temperature curing paint keeping its photocatalytic performance even if it is used for a long time, having durability in the coating itself has been desired.
In Japanese Patent Publication Laid-Open No. 67835/1996, an antifungal inorganic paint containing a photocatalyst, which is a component having a photocatalytic function as an anti-fungus agent, is proposed. However, when a photocatalyst was supported on a substrate, there was a problem concerning the limitation of the substrate or adhesion properties. Further, there was a tendency that the photocatalyst was precipitated in the paint, and the performance of the photocatalyst was not easily exhibited.
Therefore, in Japanese Patent Publication Laid Open No. 141503/1996, the improvement in a method for forming an inorganic coating having photocatalyst on the surface thereof and high photocatalytic performance is suggested. This coating has high adhesion to an inorganic substrate, however, it has poor adhesion to the surface of plastic or a material coated with an organic substance. Further, a coating of the above-mentioned inorganic coating lacks in smoothness on the surface, therefore there was a drawback that dirt is easily adhered.
Further, when a paint containing a photocatalyst is directly applied to the surface of an organic substrate or a substrate coated with an organic substance, there was a problem that said substrate was easily deteriorated due to the action of the photocatalyst.